Influence of blockade at specific levels of the coagulation cascade on restenosis in a rabbit atherosclerotic femoral artery injury model

Lipoprotein(a) in Atherosclerotic Diseases: From Pathophysiology to Diagnosis and Treatment

Lipoprotein(a) (Lp(a)) is a low-density lipoprotein (LDL) cholesterol-like particle bound to apolipoprotein(a). Increased Lp(a) levels are an independent, heritable causal risk factor for atherosclerotic cardiovascular disease (ASCVD) as they are largely determined by variations in the Lp(a) gene (LPA) locus encoding apo(a). Lp(a) is the preferential lipoprotein carrier for oxidized phospholipids (OxPL), and its role adversely affects vascular inflammation, atherosclerotic lesions, endothelial function and thrombogenicity, which pathophysiologically leads to cardiovascular (CV) events. Despite this crucial role of Lp(a), its measurement lacks a globally unified method, and, between different laboratories, results need standardization. Standard antilipidemic therapies, such as statins, fibrates and ezetimibe, have a mediocre effect on Lp(a) levels, although it is not yet clear whether such treatments can affect CV events and prognosis. This narrative review aims to summarize knowledge regarding the mechanisms mediating the effect of Lp(a) on inflammation, atherosclerosis and thrombosis and discuss current diagnostic and therapeutic potentials.

A Review of Antithrombotic Treatment in Critical Limb Ischemia After Endovascular Intervention

Endovascular intervention is often used to treat critical limb ischemia (CLI). Post-intervention treatment with antiplatelet and/or anticoagulant therapy has reduced morbidity and mortality due to cardiovascular complications. The purpose of this review is to shed light on the various pharmacologic treatment protocols for treating CLI following endovascular procedures. We reviewed the literature comparing outcomes after antithrombotic treatment for patients with CLI. We characterized antithrombotic therapies into three categories: (1) mono-antiplatelet therapy (MAPT) vs. dual antiplatelet therapy (DAPT), (2) MAPT vs. antiplatelet (AP) + anticoagulant (AC) therapy, and (3) AC vs. AP + AC therapy. Relevant results and statistics were extracted to determine differences in the rates of the following outcomes: (1) re-stenosis, (2) occlusion, (3) target limb revascularization (TLR), (4) major amputation, (5) major adverse cardiac events, (6) all-cause death, and (7) bleeding. Studies suggest that DAPT reduces post-surgical restenosis, TLR, and amputation for diabetic patients, without increasing major bleeding incidences, compared to MAPT. Also, AP + AC therapy provides overall superior efficacy, with no difference in bleeding incidences, compared to antiplatelet alone. Additionally, the effects were significant for restenosis, limb salvage, survival rates, and cumulative rate of above ankle amputation or death. These results suggest that treatment with DAPT and AP + AC might provide better outcomes than MAPT following the endovascular intervention for CLI, and that the ideal treatment may be related to the condition of the individual patient. However, the studies were few and heterogenous with small patient populations. Therefore, further large controlled studies are warranted to confirm these outcomes.

Bolus injections of novel thrombogenic site-targeted fusion proteins comprising annexin-V and Kunitz protease inhibitors attenuate intimal hyperplasia after balloon angioplasty

BACKGROUND

Systemic administrations of conventional antithrombotics reduce neointima formation after angioplasty in experimental animals. However, clinical translation of these results has not been successful due to high risk for bleeding.

OBJECTIVES

We sought to determine whether novel annexin-V (ANV)-Kunitz protease inhibitor fusion proteins, TAP-ANV and ANV-6L15, can specifically target to vascular injury site and limit neointima formation without inducing systemic hypo-coagulation in a rat carotid artery balloon angioplasty injury model.

METHODS

Near infrared imaging was carried out after balloon-injury and injection of fluorescent ANV or ANV-6L15 to examine their bio-distributions. For peri-procedure treatment, TAP-ANV or ANV-6L15 was administered as i.v. boluses 3 times: 30-minutes before balloon-injury, immediate after procedure, and 120-minutes post-balloon-injury. For extended treatment, additional i.v. bolus injection was given on day-2, day-3 and every other day thereafter. Carotid arteries were collected on day-7 and day-14 for analysis. Blood was collected for measurement of clotting parameters.

RESULTS

Near infrared imaging and immunochemistry showed that fluorescent ANV and ANV-6L15 specifically localized to injured carotid artery and significant amount of ANV-6L15 remained bound to the injured artery after 24-h. Peri-procedure injections of TAP-ANV or ANV-6L15 resulted in decrease of intima/media ratio by 56%. Extended injections of both yielded similar results. Both decreased the expression of PCNA on day-7 and increased the expression calponin on day-14 in the intima post-balloon-injury.

CONCLUSIONS

TAP-ANV and ANV-6L15 can specifically localize to balloon injured carotid arteries after i.v. bolus injections, resulting in substantial attenuation of intimal hyperplasia without inducing a state of systemic hypo-coagulation.

Factor Xa Signaling Contributes to the Pathogenesis of Inflammatory Diseases

The coagulation protease Factor Xa (FXa) triggers a variety of signaling pathways through activation of protease-activated receptors (PARs) and non-PAR receptors. FXa-mediated signaling is strongly implicated in the pathogenesis of several inflammatory diseases including fibrosis, cardiovascular diseases, and cancer. Thus, targeting of FXa can have great clinical significance in terms of the treatment of these disorders. This review summarizes the current knowledge about the mechanism of FXa signaling in cellular and animal systems under (patho) physiological conditions for a better understanding and hence a better management of FXa-induced disorders. J. Cell. Physiol. 232: 1966-1970, 2017. © 2016 Wiley Periodicals, Inc.

Discovery methodology for the development of direct factor VIIa inhibitors

INTRODUCTION

Heparin and warfarin have historically been the only antithrombotics available. Recently, however, newer anticoagulants have been developed. Factor VIIa (fVIIa) inhibitors represent one of the new and potentially exciting classes of anticoagulants currently under development. Indeed, several methodologies have been used to develop fVIIa inhibitors.

AREAS COVERED

The authors highlight some of the methologies applied for the discovery of fVIIa inhibitors including phage display, isolation of endogenous peptides from hematophagous animals and the use of the 1,5-benzothiazepine molecular scaffolds and screens of large chemical libraries previously used to identify other serine protease inhibitors. Although these screens were intended to identify thrombin and factor Xa inhibitors, the compounds often had concomitant fVIIa activity. The authors also discuss the utilization of medical chemistry techniques for the discovery of these compounds.

EXPERT OPINION

FVIIa inhibitors represent a viable option for the development of new anticoagulants. There are theoretical advantages that fVIIa inhibitors may possess over existing anticoagulants and highly specific inhibitors that possess oral bioavailability and low bleeding risk may succeed.

The role of tissue factor pathway inhibitor in atherosclerosis and arterial thrombosis

Tissue factor pathway inhibitor (TFPI) is the main inhibitor of tissue factor (TF)-mediated coagulation. In atherosclerotic plaques TFPI co-localizes with TF, where it is believed to play an important role in attenuating TF activity. Findings in animal models such as TFPI knockout models and gene transfer models are consistent on the role of TFPI in arterial thrombosis as they reveal an active role for TFPI in attenuating arterial thrombus formation. In addition, ample experimental evidence exists indicating that TFPI has inhibitory effects on both smooth muscle cell migration and proliferation, both which are recognized as important pathological features in atherosclerosis development. Nonetheless, the clinical relevance of these antithrombotic and atheroprotective effects remains unclear. Paradoxically, the majority of clinical studies find increased instead of decreased TFPI antigen and activity levels in atherothrombotic disease, particularly in atherosclerosis and coronary artery disease (CAD). Increased TFPI levels in cardiovascular disease might result from complex interactions with established cardiovascular risk factors, such as hypercholesterolemia, diabetes and smoking. Moreover, it is postulated that increased TFPI levels reflect either the amount of endothelial perturbation and platelet activation, or a compensatory mechanism for the increased procoagulant state observed in cardiovascular disease. In all, the prognostic value of plasma TFPI in cardiovascular disease remains to be established. The current review focuses on TFPI in clinical studies of asymptomatic and symptomatic atherosclerosis, coronary artery disease and ischemic stroke, and discusses potential atheroprotective actions of TFPI.

Protein anticoagulants targeting factor VIIa-tissue factor complex: a comprehensive review

Anticoagulants are pivotal for the treatment of debilitating thromboembolic and associated disorders. Current anticoagulants such as heparin and warfarin are non-specific and have a narrow therapeutic window. These limitations have provided the impetus to develop new anticoagulant therapies/strategies that target specific factors in the blood coagulation cascade, ideally those located upstream in the clotting process. Factor VIIa (FVIIa) presents an attractive target as it, in complex with tissue factor (TF), acts as the prima ballerina for the formation of blood clot. A comprehensive review delineating the structure-activity relationship of protein/peptide anticoagulants targeting FVIIa or TF-FVIIa complex is absent in the literature. In this article, we have addressed this deficit by appraising the peptide/protein anticoagulants that target FVIIa/TF-FVIIa complex. Further, the current status of these anticoagulants, with regard to their performance in different clinical trials has also been presented. Lastly, the unexplored domains of these unique proteins have also been highlighted, which will facilitate further translational research in this paradigm, to improve strategies to counter and treat thromboembolic disorders.

Changes in ADMA and TAFI levels after stenting in coronary artery disease patients

The aim of this study was to examine the contribution of asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS) and a novel marker of vascular endothelial dysfunction, and thrombin-activatable fibrinolysis inhibitor (TAFI), a risk factor for venous thrombosis, to the predisposition of coronary restenosis following stent implantation in coronary artery disease (CAD) patients. Thirty-seven patients with CAD were recruited from the Kobry El Obba Military Hospital, Cairo, Egypt. The patients were hospitalized for coronary angiography and coronary stenting (CS). Overnight fasting blood samples were collected from patients prior to CS and four months later for the determination of plasma ADMA and TAFI levels. The patients underwent follow-up coronary angiography to reveal in-stent restenosis. The results showed that plasma ADMA levels in CAD patients were significantly higher than those reported for healthy subjects. ADMA levels were significantly increased by 30% in CAD patients four months following CS. CAD patients who developed in-stent restenosis had a 35% increase in ADMA levels following CS. TAFI levels were not significantly changed after CS in CAD patients or in any of the subgroups. In conclusion, ADMA, but not TAFI, is linked to the predisposition of in-stent restenosis following CS.

New antithrombotic drugs: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

This article focuses on new antithrombotic drugs that are in or are entering phase 3 clinical testing. Development of these new agents was prompted by the limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this article (1) outlines the rationale for development of new antithrombotic agents; (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs; and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.

Evaluation of plaque stability of advanced atherosclerotic lesions in apo E-deficient mice after treatment with the oral factor Xa inhibitor rivaroxaban

Aim. Thrombin not only plays a central role in thrombus formation and platelet activation, but also in induction of inflammatory processes. Activated factor X (FXa) is traditionally known as an important player in the coagulation cascade responsible for thrombin generation. We assessed the hypothesis that rivaroxaban, a direct FXa inhibitor, attenuates plaque progression and promotes stability of advanced atherosclerotic lesions in an in vivo model. Methods and Results. Rivaroxaban (1 or 5 mg/kg body weight/day) or standard chow diet was administered for 26 weeks to apolipoprotein E-deficient mice (n = 20 per group) with already established atherosclerotic lesions. There was a nonsignificant reduction of lesion progression in the high-concentration group, compared to control mice. FXa inhibition with 5 mg Rivaroxaban/kg/day resulted in increased thickness of the protective fibrous caps (12.3 ± 3.8 μm versus 10.1 ± 2.7 μm; P < .05), as well as in fewer medial erosions and fewer lateral xanthomas, indicating plaque stabilizing properties. Real time-PCR from thoracic aortas revealed that rivaroxaban (5 mg/kg/day) treatment reduced mRNA expression of inflammatory mediators, such of IL-6, TNF-α, MCP-1, and Egr-1 (P < .05). Conclusions. Chronic administration of rivaroxaban does not affect lesion progression but downregulates expression of inflammatory mediators and promotes lesion stability in apolipoprotein E-deficient mice.

Blood coagulation factor Xa as an emerging drug target

INTRODUCTION

Factor (F)Xa is well-known as an important player in the coagulation cascade responsible for thrombin generation. More recently, FXa emerged as an essential player in cell biology via activation of protease-activated receptors (PAR)-1 and -2. This pleiotropic role of FXa forms the basis for its potential contribution to the pathogenesis of several diseases.

AREAS COVERED

The role of FXa in pathophysiology is reviewed with special emphasis on its signal transduction properties. To this end, we first discuss the important role of FXa in the coagulation cascade, we continue with recent data on FXa induced signaling in pathophysiology with special emphasis on tissue remodeling and fibrosis and discuss the potential of FXa as an emerging drug target.

EXPERT OPINION

FXa is more than a passive intermediate in the coagulation cascade and FXa may in fact orchestrate fundamental processes during pathophysiology. Targeting FXa may be an exciting new therapeutic strategy in the treatment of (fibro)proliferative diseases for which current treatment options are limited.

Delivery of TFPI-2 using ultrasound with a microbubble agent (SonoVue) inhibits intimal hyperplasia after balloon injury in a rabbit carotid artery model

Here we report a new, simple and efficient method by using ultrasound and a microbubble agent (SonoVue) for delivering a gene to balloon-injured carotid arteries for restenosis prophylaxis. The tissue factor pathway inhibitor-2 (TFPI-2) has been shown to inhibit the postinjury intimae hyperplasia in atherosclerotic vessels. New Zealand white rabbits were divided into 4 groups with 14 in each, a treatment control for balloon injury, a gene vehicle control, a gene delivery of TFPI-2 without using ultrasound and a gene delivery of TFPI-2 using ultrasound. After four weeks, the injured artery neointimal proliferation was significantly lower in the TFPI-2 group with ultrasound than the control groups (p < 0.01) according to the measurement of the mean luminal diameters by B-mode ultrasonography. The ratio of intimal/media area and the stenosis rate in the gene delivery facilitated by ultrasound were significantly lower than those of the nonultrasound gene delivering method (p < 0.01).

Tissue Factor/Factor FVII Complex Inhibitors in Cardiovascular Disease. Are Things Going Well?

Blood coagulation is a complex biological mechanism aimed to avoid bleeding in which a highly regulated and coordinated interplay of specific proteins and cellular components respond quickly to a vascular injury. However, when this mechanisms occurs in the coronary circulation, it has not a "protective" effect, but rather, it plays a pivotal role in determining acute coronary syndromes. Coagulation recognizes Tissue Factor (TF), the main physiological initiator of the extrinsic coagulation pathway, as its starter.Since TF:VIIa complex is the critical point of the blood coagulation cascade, it is a pharmacological attractive issue for the development of agents with anti thrombotic properties that can exert their activity by inhibiting complex formation and/or its catalytic activity. In fact, it is intuitive that an antithrombotic agent able to inhibit this initial step of the coagulation pathway has several theoretical, extremely important, advantages if compared with drugs active downstream the coagulation pathway, such as FXa or thrombin. The present report gives a brief overview of TF pathophysiology, highlighting the most recent advances in the field of inhibitors of the complex TF/VIIa potentially useful in cardiovascular disease.

Tissue factor in cardiovascular disease pathophysiology and pharmacological intervention

Tissue factor (TF) is the major trigger of the coagulation cascade and thereby crucially involved in the maintenance of vascular hemostasis. By binding factor VIIa, the resulting TF:VIIa complex activates the coagulation factors IX and X ultimately leading to fibrin and clot formation. In the vessel wall, TF expression and activity is detectable in vascular smooth muscle cells and fibroblasts and, at a much lower level, in endothelial cells and can be induced by various stimuli including cytokines. In addition, TF is found in the bloodstream in circulating cells such as monocytes, in TF containing microparticles, and as a soluble splicing isoform. Besides its well-known extracellular role as a trigger of coagulation, TF also functions as a transmembrane receptor, and TF-dependent intracellular signaling events regulate the expression of genes involved in cellular responses such as proliferation and migration. TF indeed appears to be involved in the pathogenesis of neointima formation and tumor growth, and increased levels of TF have been detected in patients with cardiovascular risk factors or coronary artery disease as well as in those with cancer. Therefore, pharmacological or genetic inhibition of TF may be an attractive target for the treatment of cardiovascular disease and cancer. Different strategies for inhibition of TF have been developed such as inhibition of TF synthesis and blockade of TF action. Clinical applications of such strategies need to be tested in appropriate trials, in particular for evaluating the advantages of targeted versus systemic delivery of the inhibitors.

Tissue factor pathway inhibitor, vascular risk factors and subclinical atherosclerosis: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Tissue factor pathway inhibitor (TFPI) is an endothelial membrane-associated anticoagulant protein. Higher circulating levels might reflect endothelial damage.

OBJECTIVE

We hypothesized an association of higher total TFPI with subclinical atherosclerosis.

PATIENTS/METHODS

Total TFPI was measured in 1000 participants of the Multi-Ethnic Study of Atherosclerosis, a cohort of 6814 men and women without clinical vascular disease, aged 45-84, from four ethnic groups. Subclinical atherosclerosis measures were coronary artery calcium (CAC), carotid intima-media thickness (IMT) and ankle-brachial index (ABI).

RESULTS

TFPI was higher with age, male gender, higher LDL-cholesterol, smoking and diabetes, but not ethnicity. Adjusting for risk factors, TFPI in the 4th quartile versus 1st quartile was associated with a 1.2-fold increased risk of detectable CAC (95% CI 1.0-1.4), a 2.1-fold increased risk of CAC >400 Agatston units (95% CI 1.1-4.0) and a 1.6-fold (95% CI 1.1-2.5) increased risk of internal carotid IMT above the 80th percentile, but not with external carotid IMT or low ABI. Findings were consistent across ethnic groups.

CONCLUSIONS

In this diverse population, higher total TFPI was associated with prevalent CAC (limited to levels >400 units), and elevated internal carotid IMT, independent of other factors. Higher TFPI may indicate endothelial dysfunction. Further study is needed of TFPI and progression of atherosclerosis.

Thrombin induces fibronectin-specific migration of pulmonary microvascular endothelial cells: requirement of calcium/calmodulin-dependent protein kinase II

Pulmonary arterial hypertension (PAH) is a progressive disease of excess vasoconstriction and vascular cell proliferation that results in increased pulmonary vascular resistance and right heart failure. We have previously shown (66) that tissue factor expression is increased in the abnormal vessels of patients and rats with PAH. We hypothesized that tissue factor and its downstream mediator, thrombin, would promote migration of endothelial cells (EC) and the vascular pathology of PAH. Immunostaining revealed EC and a fibronectin-enriched matrix within the "plexiform-like" lesions in a rat model of severe PAH. In a modified Boyden assay, protease-activated receptor 1 (PAR1; thrombin receptor) stimulation by agonist peptide or thrombin induced pulmonary microvascular EC (PMVEC) migration when the cells were interacting with fibronectin, but not with other extracellular matrix proteins. Thrombin/fibronectin-induced migration was confirmed in wound healing and angiogenesis assays and was abrogated by the PAR1 antagonist SCH79797 and soluble RGD peptide. This fibronectin dependence was unique to PAR1 activation; other EC agonists evaluated did not induce migration on any matrix, and 10% FBS stimulated similar levels of migration on all matrix proteins tested. Thrombin/fibronectin stimulated autophosphorylation of calcium/calmodulin dependent protein kinase II (CaMKII) in PMVEC, and inhibitors of CaMKII blocked thrombin-induced migration on fibronectin, but had no effect on migration induced by 10% FBS. In contrast, EC isolated from the proximal pulmonary artery migrated in response to most agonists independent of the matrix substrate. Our findings illustrate EC heterogeneity in a single tissue and indicate a novel role for CaMKII in mediating EC migration. Because PMVEC have been shown to have impressive proliferative potential, thrombin/fibronectin-stimulated migration of these cells to a site of injured endothelium is a potential mechanism by which thrombin contributes to the development of vascular lesions in PAH.

New antithrombotic drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This chapter focuses on new antithrombotic drugs that are in phase II or III clinical testing. Development of these new agents was prompted by limitations of existing antiplatelet, anticoagulant, or fibrinolytic drugs. Addressing these unmet needs, this chapter (1) outlines the rationale for development of new antithrombotic agents, (2) describes the new antiplatelet, anticoagulant, and fibrinolytic drugs, and (3) provides clinical perspectives on the opportunities and challenges faced by these novel agents.

Downregulation of tissue factor (TF) by RNA interference induces apoptosis and impairs cell survival of primary endothelium and tumor cells

Tissue factor (TF) has been implicated in the thrombotic complications seen during vascular rejection of allografts and may contribute to intimal hyperplasia in chronic allograft vasculopathy. Downregulation of endothelial TF expression post-transplantation could therefore be of therapeutic value. Lentivirus-mediated RNA interference was used in primary endothelial cells (EC) to investigate its effects on TF protein expression and functional activity. Lentivirus-mediated expression of a TF-specific short-interfering (si) RNA with green fluorescent protein as a reporter gene (siRNATF-GFP) resulted in a 42 +/- 3.9% reduction in EC surface-expressed TF as compared with cells expressing a scrambled siRNATF sequence (P = 0.025). The TF content in EC lysates was reduced from 6.85 +/- 1.99 ng to 3.05 +/- 0.82 ng (P = 0.006). Factor X (FX) activation was not impaired on the apical EC surface. The subendothelial matrix of ECs with low TF expression showed significantly reduced TF activity compared with non-transduced cells or with cells harboring the empty vector. ECs expressing siRNATF-GFP exhibited reduced reporter gene (GFP) expression and cell density and an altered morphology. Transfection of control cells with high (J82 cells) or low (MiaPaCa-2 cells) TF expression with siRNATF oligonucleotides caused apoptosis of the J82 but not of the MiaPaCa-2 cells. Thus, lentivirus-mediated RNA interference reduces the TF expression of activated ECs but does not affect FX activation by TF/FVIIa expressed on the apical surface. The downregulation has nevertheless substantial negative effects on the viability of ECs and TF-expressing control cells. These findings imply that certain levels of TF are required for the maintained viability and growth of endothelium and TF-expressing tumor cells.

Unchecked thrombin is bad news for troubled arteries

Thrombin is clearly a key trigger of thrombosis, the proximal cause of most morbidity and mortality in atherosclerotic cardiovascular disease. Might thrombin also contribute to longer-term, structural changes in the arterial wall that promote narrowing and clotting? A study in this issue of the JCI argues that it can. Aihara et al. report that haploinsufficiency of heparin cofactor II, a glycosaminoglycan-dependent thrombin inhibitor, exacerbates injury- or hyperlipidemia-induced arterial lesion formation in mice, possibly by excessive thrombin signaling through protease-activated receptors (see the related article beginning on page 1514).

The status of new anticoagulants

Currently available anticoagulants include heparin, low-molecular weight heparin, fondaparinux and warfarin. Despite advances with low-molecular weight heparin and fondaparinux, the currently available agents have limitations that have provided the impetus for the development of new drugs for prevention and treatment of both venous and arterial thromboembolism. Novel anticoagulants targeting specific steps in coagulation are in various stages of development. This paper reviews the pharmacology of these new agents and describes the results of clinical trials with new anticoagulants in more advanced stages of clinical testing.

Inhibition of tissue factor as a novel approach to anticoagulation in patients with coronary artery disease

Anticoagulation, aimed at mitigating the enlargement of obstructive thrombi in coronary arteries, is a cornerstone of treatment for patients with unstable coronary artery disease. Limitations of currently available pharmacologic agents have sustained substantial interest in discovering novel anticoagulants that may more effectively and safely dampen the activation and perpetuation of the coagulation cascade that contributes to acute coronary syndromes. Tissue factor plays a critical role in initiating the molecular events leading to thrombus formation and thus is an attractive target to inhibit blood coagulation at the most proximal level, quenching the effect of downstream amplification that occurs in the coagulation cascade. Recent studies demonstrating the safety and efficacy of inhibiting tissue factor for reducing thrombin generation in patients with coronary artery disease support the promise of this class of novel anticoagulants for the treatment of acute coronary syndromes.

Identification and characterization of murine alternatively spliced tissue factor

Tissue factor (TF) is a transmembrane glycoprotein that initiates coagulation and plays a critical role in regulating hemostasis and thrombosis. We have recently reported a naturally occurring, soluble form of human tissue factor (asTF) generated by alternative splicing. This splice variant has a novel C-terminus with no homology to that of the full-length TF (flTF), lacks a transmembrane domain, and is active in the presence of phospholipids. Mouse models offer unique opportunities to examine the relative importance of flTF and asTF in mediating thrombosis, the response to arterial injury, and ischemic damage. To that end, we have identified and characterized murine asTF (masTF). Like the human splice variant, masTF lacks a transmembrane domain and has a unique C-terminus. We have generated antibodies specific to masTF and murine flTF (mflTF) to examine the expression of both forms of TF. masTF antigen is widely and abundantly expressed, with a pattern similar to that of mflTF, in adult tissues, in experimentally induced thrombi, and during development. These studies demonstrate that masTF contributes to the pool of total TF and may thus play an important role in mediating TF-dependent processes.

Differential expression of tissue factor (TF) in calcineurin inhibitor-induced nephrotoxicity and rejection—implications for development of a possible diagnostic marker

Deposition of fibrin in the form of fibrinoid necrosis is a common feature of severe acute renal allograft rejection. The role of the coagulation system and its initiator tissue factor (TF) during this process is, however, still poorly understood. In this study, we analyzed the expression of TF in 88 renal transplants afflicted with different forms of rejection and calcineurin inhibitor-induced nephrotoxicity, to see whether there was differential expression of this protein. TF immunoreactivity was evaluated semiquantitatively in six different renal structures: the podocytes, Bowman epithelium, the endothelium of the glomeruli, the brush border of tubular cells, the thin ascending loop of Henle, and small arteries/arterioles. The TF expression of normal renal tissue (n=6) was restricted to the glomerular podocytes and Bowman epithelium, and to some extent the ascending loop of Henle. Renal allografts undergoing acute rejection (AR) of grades I-III, (n=13, n=17 and n=12, respectively) did not show any altered TF expression in the glomeruli or vascular endothelium. In the ascending loop of Henle, a reduced expression could be seen (ARI, p=0.015; and ARII, p=0.043). TF staining of the brush border of renal transplants undergoing acute cyclosporin A (CsA) nephrotoxicity (n=18) was significantly higher than in normal kidneys (p=0.0003), as well as in transplants undergoing various degrees of acute rejection (ARI, p=0.027; ARII, p=0.0012; and ARIII, p=0.0001). Tubular brush border-expressed TF was also evident in 10 of 15 allografts suffering from chronic CsA nephrotoxicity, compared to 4 out of 13 cases with chronic allograft vasculopathy (CAV), but the increase was not statistically significant relative to normal kidneys. The majority of the grafts afflicted with either of the two chronic conditions displayed a TF-positive arterial endothelium (CAV, p=0.0034; and chronic CsA nephrotoxicity, p=0.0026) relative to controls. In conclusion, these results indicate that vascular TF expression is not altered during acute rejection, but may be of importance in chronic allograft nephropathy. Furthermore, TF immunoreactivity in the tubular brush border may be specific to acute CsA nephrotoxicity and might be used as a biomarker for this condition. Further studies are required to evaluate the possible role of brush border-expressed TF in the pathogenesis of CsA nephrotoxicity.

New anticoagulants

The limitations of heparin and warfarin have prompted the development of new anticoagulant drugs for prevention and treatment of venous and arterial thromboembolism. Novel parenteral agents include synthetic analogs of the pentasaccharide sequence of heparin that mediates its interaction with antithrombin. Fondaparinux, the first synthetic pentasaccharide, is licensed for prevention of venous thromboembolism (VTE) after major orthopedic surgery and for initial treatment of patients with VTE. Idraparinux, a long-acting pentasaccharide that is administered subcutaneously once-weekly, is being compared with warfarin for treatment of VTE and for prevention of cardioembolic events in patients with atrial fibrillation. New oral anticoagulants include direct inhibitors of thrombin, factor Xa and factor IXa. Designed to provide more streamlined anticoagulation than warfarin, these agents can be given without routine coagulation monitoring. Ximelagatran, the first oral direct thrombin inhibitor, is as effective and safe as warfarin for prevention of cardioembolic events in patients with atrial fibrillation. However, ximelagatran produces a three-fold elevation in alanine transaminase levels in 7.9% of patients treated for more than a month, the long-term significance of which is uncertain. Whether other direct thrombin inhibitors or inhibitors of factors Xa or IXa also have this problem is under investigation. After a brief review of coagulation pathways, this paper focuses on new anticoagulants in advanced stages of clinical testing.

New anticoagulant therapy

The development of new anticoagulants is expanding the list of drugs that can be used to prevent and treat venous and arterial thrombosis. New parenteral anticoagulants have been developed to overcome the limitations of heparin and low-molecular-weight heparin, whereas novel orally active anticoagulants have been designed to provide more streamlined therapy than vitamin K antagonists. This review identifies the molecular targets of new anticoagulants, describes the results of clinical trials, and provides clinical perspective on the opportunities for new anticoagulants.

Fusion proteins comprising annexin V and Kunitz protease inhibitors are highly potent thrombogenic site-directed anticoagulants

The anionic phospholipid, phosphatidyl-L-serine (PS), is sequestered in the inner layer of the plasma membrane in normal cells. Upon injury, activation, and apoptosis, PS becomes exposed on the surfaces of cells and sheds microparticles, which are procoagulant. Coagulation is initiated by formation of a tissue factor/factor VIIa complex on PS-exposed membranes and propagated through the assembly of intrinsic tenase (factor VIIIa/factor IXa), prothrombinase (factor Va/factor Xa), and factor XIa complexes on PS-exposed activated platelets. We constructed a novel series of recombinant anticoagulant fusion proteins by linking annexin V (ANV), a PS-binding protein, to the Kunitz-type protease inhibitor (KPI) domain of tick anticoagulant protein, an aprotinin mutant (6L15), amyloid beta-protein precursor, or tissue factor pathway inhibitor. The resulting ANV-KPI fusion proteins were 6- to 86-fold more active than recombinant tissue factor pathway inhibitor and tick anticoagulant protein in an in vitro tissue factor-initiated clotting assay. The in vivo antithrombotic activities of the most active constructs were 3- to 10-fold higher than that of ANV in a mouse arterial thrombosis model. ANV-KPI fusion proteins represent a new class of anticoagulants that specifically target the anionic membrane-associated coagulation enzyme complexes present at sites of thrombogenesis and are potentially useful as antithrombotic agents.

New anticoagulants: beyond heparin, low-molecular-weight heparin and warfarin

The limitations of traditional anticoagulants, heparin and warfarin, have prompted the development of new anticoagulant drugs for prevention and treatment of both venous and arterial thromboembolism. After a brief review of thrombogenesis and its regulation, this paper focuses on new anticoagulant agents in more advanced stages of clinical testing.

Recombinant TFPI and variants:potential implications in the treatment of cardiovascular disorders

The Kunitz-type proteinase inhibitor, tissue factor pathway inhibitor (TFPI), is the only endogenous inhibitor of the tissue factor (TF)-mediated coagulation pathway that plays a dominant role in normal haemostasis. TFPI exerts its action by binding to factor Xa (FXa) forming a TFPI-FXa complex that then, in a second step, binds and effectively inhibits the TF-factor VIIa (FVIIa) complex. Both full-length TFPI and chemically modified forms (e.g., truncated, glycosylated or phosphorylated TFPI variants) exert various pharmacological effects. The anticoagulant and antiplatelet actions of TFPI, its potency in inhibiting thrombin and FXa generation, as well as its favourable antithrombotic effectiveness seen in different animal models of venous and arterial thrombosis make this inhibitor a promising agent that could be potentially useful in several clinical indications. The inhibitory action of TFPI is accelerated by heparin. Heparin, as well as low molecular weight heparin (LMWH) derivatives, release TFPI from the vascular endothelium, an effect which seems to contribute mainly to the antithrombotic effectiveness of these drugs. The clinical relevance of TFPI is still undefined. Based on the beneficial actions in animal studies, as well as on the results obtained in first clinical investigations, TFPI is expected to be effective in the treatment of various diseases, such as disseminated intravascular coagulation, sepsis, coronary syndromes, stroke and acute respiratory distress syndrome (ARD). Further clinical trials should clarify the role of TFPI and more importantly define its potential usefulness as a prophylactic and/or therapeutic agent.

The therapeutic potential of novel anticoagulants

Conventional anticoagulant therapy has been based on indirect inhibition of coagulation factors with heparin and warfarin. These agents display liabilities prompting the development of new anticoagulants over the last two decades. The first to be developed was a series of low molecular weight heparins(LMWHs). Their favourable pharmacokinetic profiles and risk/benefit ratios led to widespread use in Europe and, more recently, approval for their use in the USA. Paralleling the development of LMWHs has been the pursuit of a different strategy focused on direct rather than indirect inhibition of enzymes in the coagulation cascade. In contrast to heparin, LMWHs, or other glycosaminoglycans, direct inhibitors exert their effects independent of either antithrombin III (ATIII) or heparin cofactor II (HCII) and more effectively inhibit clot-bound thrombin or FXa. Highly potent, selective (versus other serine proteases)direct thrombin and FXa inhibitors have been identified and isolated from natural sources, such as leeches, ticks and hookworms. The recombinant forms and analogues of the senatural proteins have been produced using molecular biology techniques, i.e., rHirudin, Hirulogs, recombinant tick anticoagulant peptide (rTAP), recombinant antistasin (rATS) and recombinant nematode anticoagulant peptide-5 (rNAP-5). The design of novel structures or the modification of existing chemicals has led to the synthesis of many non-peptide, low molecular weight inhibitors of thrombin and FXa. Some of them are orally active and may be suitable for long-term clinical use. In addition, considerable progress has been made in developing specific TF/VIIa complex inhibitors. The anticoagulation properties of the new agents are being characterised in experimental studies. Some of them have been advanced to large scale clinical trials and their effectiveness, and sometimes relative ineffectiveness,in arterial and venous thromboembolic disorders has been demonstrated. They are being tested for their potential as new antithrombotic agents that act via direct enzyme inhibition. Thus,the clinician should in future be able to target different thrombotic conditions with proven, specific anticoagulant interventions.

Role of oxidatively modified low density lipoproteins and anti-oxidants in atherothrombosis

Retrospective studies have demonstrated an association between coronary artery disease (CAD) and increased plasma levels of oxidised low density lipoproteins (LDL). A very recent prospective study in heart transplant patients has demonstrated that oxidised LDL is an independent risk factor for transplant CAD, thus further supporting the hypothesis that oxidised LDL is actively involved in the development of CAD. The increase of circulating oxidised LDL is most probably caused by back-diffusion from the atherosclerotic arterial wall in the blood, independent of plaque rupture. Indeed, plasma levels of oxidised LDL were very similar in patients with stable CAD and in patients with acute coronary syndromes. These were, however, associated with increased release of malondialdehyde (MDA)-modified LDL. Oxidised LDL may be generated by radical-mediated or by lipoxygenase or phospholipase catalysed lipid oxidation, and by myeloperoxidase catalysed protein and lipid oxidation. Prostaglandin synthesis by endothelial cells under oxidative stress and platelet activation are associated with the release of aldehydes; these induce the oxidative modification of the apolipoprotein B-100 moiety of LDL in the absence of lipid peroxidation, and thus generate MDA-modified LDL. Efficient prevention of in vivo oxidation may involve efficient cholesterol lowering, improving the anti-oxidative status of LDL by increasing the anti-oxidant content and increasing the oleate content of LDL, and by shifting the LDL away from phenotype B (characterised by small dense LDL particles). Anti-oxidative and anti-inflammatory enzymes associated with HDL may inhibit the oxidation of LDL or reverse the atherothrombotic effects of LDL.

Thr325Ile polymorphism of the TAFI gene is related to TAFI antigen plasma levels and angiographic restenosis after percutaneous coronary interventions

BACKGROUND

The fibrinolytic system is closely related to several processes that are involved in restenosis. We have previously shown that high pre-procedural plasma levels of thrombin-activatable fibrinolysis inhibitor (TAFI) antigen predicted angiographic restenosis. The aims of this study were to evaluate the relationship between Thr325Ile polymorphisms, plasma levels of TAFI antigen, and late angiographic restenosis after percutaneous coronary intervention (PCI).

METHODS

We prospectively studied 159 patients with stable angina who underwent successful elective angioplasty or stenting of de novo native coronary artery lesions. Blood samples were drawn before the procedure. TAFI antigen levels were measured, as well as the presence of TAFI Ile325Thr genetic variation. Follow-up coronary angiography was performed in 90% of patients.

RESULTS

The genotypes based on Ile325Thr substitution had significantly different TAFI antigen levels: genotype C/C>C/T>T/T (111+/-29%, 87+/-24%, and 59+/-22%, respectively, p<0.006). T/T genotype was associated with lower rates of restenosis compared to C/T and C/C genotypes (25% versus 37% and 33%, respectively, p<0.05).

CONCLUSIONS

These data suggest that plasma TAFI antigen levels are genetically controlled. The T/T Thr325Ile polymorphism of the TAFI gene is associated with lower plasma levels of TAFI antigen and lower restenosis rates after PCI.

Active-site inactivated FVIIa decreases thrombosis and necrosis in a random skin flap model of acute ischemia

BACKGROUND

Previous studies have emphasized the role of ischemia in inducing vascular thrombosis.

MATERIALS AND METHODS

Using a skin flap model of acute ischemia in the rat, we studied the effect of active-site inactivated factor VIIa (FVIIai), an inhibitor of tissue factor (TF), on tissue survival during acute ischemia.

RESULTS

Ribonuclease protection analysis revealed an increase in TF in ischemic parts of the flap, and in situ hybridization localized this increase mainly to perivascular cells. A decrease in vascular thrombosis, as determined by fibrin immunostaining, was observed in FVIIai-treated animals. Intravenous administration of FVIIai had a positive impact on survival of the flap. Laser Doppler flowmetry revealed an increase in blood flow in the FVIIai-treated group. In treated animals, prothrombin time (PT) was increased (P < 0.01), whereas partial thromboplastin time (APTT) was unaltered; no significant impairment in systemic hemostasis (peri- and postoperative bleeding) was observed.

CONCLUSIONS

These findings demonstrate that TF expression is increased in perivascular cells in ischemic skin flaps and that FVIIai, by inhibiting TF, increases flap survival.

New anticoagulant drugs: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This article about new anticoagulant drugs is part of the seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. The limitations of existing oral and parenteral anticoagulant agents have prompted a search for novel agents. Focusing on new anticoagulant drugs for the prevention and treatment of arterial and venous thrombosis, this article (1) reviews arterial and venous thrombogenesis, (2) discusses the regulation of coagulation, (3) describes the pathways for testing new anticoagulant agents, (4) describes new anticoagulant strategies focusing primarily on agents in phase II or III clinical testing, and (5) provides clinical perspective as to which of these new strategies is most likely to succeed.

Inhibition of restenosis by tissue factor pathway inhibitor: in vivo and in vitro evidence for suppressed monocyte chemoattraction and reduced gelatinolytic activity

Activation of inflammatory and procoagulant mechanisms is thought to contribute significantly to the initiation of restenosis, a common complication after balloon angioplasty of obstructed arteries. During this process, expression of tissue factor (TF) represents one of the major physiologic triggers of coagulation that results in thrombus formation and the generation of additional signals leading to vascular smooth muscle cell (VSMC) proliferation and migration. In this study, we have investigated the mechanisms by which inhibition of coagulation at an early stage through overexpression of tissue factor pathway inhibitor (TFPI), an endogenous inhibitor of TF, might reduce restenosis. In a rabbit femoral artery model, percutaneous delivery of TFPI using a recombinant adenoviral vector resulted in a significant reduction of the intimamedia ratio 21 days after injury. Investigating several markers of inflammation and coagulation, we found reduced neointimal expression of monocyte chemoattractant protein-1 (MCP-1), lesional monocyte infiltration, and expression of vascular TF, matrix metalloproteinase-2 (MMP-2), and MMP-9. Moreover, overexpression of TFPI suppressed the autocrine release of platelet-derived growth factor BB (PDGF-BB), MCP-1, and MMP-2 in response to factors VIIa and Xa from VSMCs in vitro and inhibited monocyte TF activity. These results suggest that TFPI exerts its action in vivo through not only thrombotic, but also nonthrombotic mechanisms.

Tissue Factor: A Key Molecule in Hemostatic and Nonhemostatic Systems

Tissue factor (also known as tissue thromboplastin or CD142) is the protein that activates the blood clotting system by binding to, and activating, the plasma serine protease, factor VIIa, following vascular injury. Because of its essential role in hemostasis, tissue factor plays a role in pathology associated with hemostasis, triggering the coagulation system in many thrombotic diseases and the coagulopathies associated with sepsis and other forms of disseminated intravascular coagulation. Recent research has also implicated tissue factor in a variety of nonhemostatic roles, including cell signaling, inflammation, vasculogenesis, and tumor growth and metastasis. This review focuses on both the well-known roles of tissue factor in hemostasis and thrombosis and the newer concepts of tissue-factor biology including how it functions as a signaling receptor and the possible role of blood-borne tissue factor in thrombosis.

MCP-1 deficiency is associated with reduced intimal hyperplasia after arterial injury

Monocyte chemoattractant protein (MCP)-1 is abundant in smooth muscle cells (SMC) and macrophages of atherosclerotic plaques and in the injured arterial wall. MCP-1 and its receptor, CCR2, are important mediators of macrophage accumulation and atherosclerotic plaque progression. We have recently reported that CCR2(-/-) mice have a approximately 60% decrease in intimal hyperplasia and medial DNA synthesis in response to femoral arterial injury. We have now examined the response to femoral arterial injury in MCP-1(-/-) mice. MCP-1 deficiency was associated with a approximately 30% reduction in intimal hyperplasia at 4 weeks and was not associated with diminished medial DNA synthesis. Despite inducing tissue factor in SMC culture, MCP-1 deficiency was not associated with a decrease in neointimal tissue factor after injury. These data suggest that MCP-1 and CCR2 deficiencies have distinct effects on arterial injury. The effects of MCP-1 on intimal hyperplasia may be mediated largely through SMC migration.

Antiapoptotic effect of coagulation factor VIIa

Binding of factor VIIa (FVIIa) to its cellular receptor tissue factor (TF) was previously shown to induce various intracellular signaling events, which were thought to be responsible for TF-mediated biologic effects, including angiogenesis, tumor metastasis, and restenosis. To understand the mechanisms behind these processes, we have examined the effect of FVIIa on apoptosis. Serum deprivation-induced apoptosis of BHK(+TF) cells was characterized by apoptotic blebs, nuclei with chromatin-condensed bodies, DNA degradation, and activation of caspase 3. FVIIa markedly decreased the number of cells with apoptotic morphology and prevented the DNA degradation as measured by means of TdT-mediated dUTP nick end labeling (TUNEL). The antiapoptotic effect of FVIIa was confirmed by the observation that FVIIa attenuated caspase 3 activation. FVIIa-induced antiapoptotic effect was dependent on its proteolytic activity and TF but independent of factor Xa and thrombin. FVIIa-induced cell survival correlated with the activation of Akt and was inhibited markedly by the specific PI3-kinase inhibitor, LY294002. Blocking the activation of p44/42 mitogen-activated protein kinase (MAPK) by the specific mitogen-induced extracellular kinase (MEK) inhibitor, U0126, impaired modestly the ability of FVIIa to promote cell survival. In conclusion, FVIIa binding to TF provided protection against apoptosis induced by growth factor deprivation, primarily through activation of PI3-kinase/Akt pathway, and to a lesser extent, p44/42 MAPK pathway.

Overexpression of glycosyl phosphatidylinositol-anchored tissue factor pathway inhibitor-1 inhibits tissue factor activity

The cellular initiation of coagulation by the tissue factor (TF)-activated factor VII complex is transiently inhibited by endogenous tissue factor pathway inhibitor-1 (TFPI-1), whereas exogenously added TFPI-1 is targeted to a degradation pathway. This study investigates the relevance of glycosyl phosphatidylinositol (GPI) anchoring for the anticoagulant properties of TFPI-1. Experiments were performed with the human cell line ECV304 using liposomal gene transfer. For GPI anchoring of TFPI-1 we used a fusion protein of TFPI-1 and the GPI attachment sequence of decay-accelerating factor (GPI-TFPI-1), and compared it with wild-type TFPI-1. We measured TF and TFPI-1 surface expression by flow cytometry and TF proteolytic activity by a chromogenic assay for activated factor X generation. After transfection of GPI-TFPI-1, surface expression of TFPI-1 increased to 134 +/- 9% of mock transfected cells (mean +/- SEM, P = 0.004), and transfection with wild-type TFPI-1 did not significantly alter TFPI-1 surface expression. After transfection with GPI-TFPI-1, TF activity was reduced by 18 +/- 9% compared with mock transfections (P = 0.003), whereas after transfection with TFPI-1 wild type no significant inhibition was observed. This effect was not due to altered TF expression. GPI anchoring is an essential prerequisite for surface expression of TFPI-1 and inhibition of TF activity. Gene transfer of GPI-anchored TFPI, therefore, may be an efficient tool to inhibit local TF-induced coagulation.

Hirulog-like peptide reduces restenosis and expression of tissue factor and transforming growth factor-beta in carotid artery of atherosclerotic rabbits

Restenosis is responsible to approximately 30% of long-term failure following therapeutic vascular procedures. Thrombosis plays a key role in the development of restenosis. Thrombin-specific inhibitors have been considered as one type of candidates for the prevention of restenosis. Previous studies by our group demonstrated that a novel thrombin-specific inhibitor, hirulog-like peptide (HLP), reduced balloon catheter-induced neointima formation in rat carotid arteries. The present study examined the effect of HLP on angioplasty-induced restenosis in carotid arteries of atherosclerotic rabbits. New Zealand white rabbits were subject to air desiccation of the lumen of the right carotid arteries, then received high cholesterol/fat diet for 3 weeks. The rabbits were intravenously infused with HLP (1.6 mg/(kg/h)) or saline (n=7 per group) for 4 h started before angioplasty which dilated atherosclerotic lesions in right common carotid artery. Four weeks after the angioplasty, neointimal area, stenosis and neointima/media ratio in injured carotid arteries were reduced in atherosclerotic rabbits treated with HLP compared to saline controls by 62, 39 and 59% (P<0.05). The expression of tissue factor (TF) and transforming growth factor (TGF)-beta in the neointima of carotid arteries of rabbits treated with HLP was significantly weaker than saline controls (P<0.05 or <0.01). Activated partial thromboplastin time and bleeding time in HLP-treated rabbits were not significantly prolonged compared to controls. The results of the present study suggest that HLP may substantially reduce angioplasty-induced restenosis in atherosclerotic rabbits without increasing bleeding tendency. The inhibition on the expression of TF and TGF-beta in the neointima of the arterial wall may contribute to the preventive effect of HLP on restenosis in atherosclerotic rabbits.

Prolonged procoagulant activity on overstretch-injured coronary arteries in pigs

This study was designed to assess the time course and nature of the vascular procoagulant response after 1.5-fold balloon overstretch injury of the coronary arteries in pigs. Arteries were excised for chromogenic assay of bound factor (F)Xa and thrombin at 24 h, 3 days, 1 week, or 2 weeks after injury. FXa at the site of injury remained elevated for 1 week (4.9 +/- 5.9 microg cm(-2), n = 10), compared with non-injured control arteries (0.4 +/- 0.2 microg cm(-2), n = 18, P = 0.00025), while thrombin was increased only at 24 h. Tissue factor protein was abundant in non-injured coronaries (10 +/- 6 ng microg(-1) total protein, n = 9) and levels were unchanged by injury (13 +/- 11 ng microg(-1), n = 6) or 24-h administration of tissue factor pathway inhibitor (16 +/- 6 ng microg(-1), n = 6). Persistent tissue factor-mediated procoagulant activity may explain the need for prolonged anticoagulation to attenuate neointimal formation after balloon-induced coronary injury.

Involvement of C-reactive protein obtained by directional coronary atherectomy in plaque instability and developing restenosis in patients with stable or unstable angina pectoris

We investigated whether positive immunohistochemical staining of C-reactive protein (CRP) in initial culprit lesions is related to coronary plaque instability and whether it could affect the outcome of directional coronary atherectomy (DCA). The plasma level of CRP is a reliable marker of the risk of coronary events and restenosis after percutaneous coronary intervention. However, the influence of tissue CRP in atheromatous plaque on plaque vulnerability and restenosis remains unknown. Samples of DCA obtained from 12 patients with stable angina pectoris and 15 patients with unstable angina pectoris were immunohistochemically stained with a monoclonal antibody against CRP. We performed follow-up coronary angiography on 22 of 27 patients to evaluate the presence of restenosis after DCA. Immunoreactivity to CRP was localized to macrophages, smooth muscle cells, and necrotic areas. The ratio of CRP positive cells to total cells was significantly higher in DCA samples from patients with unstable (17.9 +/- 2.0%) than with stable angina (11.0 +/- 2.5%) (p <0.05). Follow-up coronary angiography showed that 12 of 22 patients developed restenosis after DCA. The ratio was also significantly higher in DCA specimens from patients with restenosis (19.3 +/- 2.8%) compared with those without restenosis (11.0 +/- 2.0%) (p <0.05). In addition, the ratio significantly correlated with late luminal loss (r = 0.428, p <0.05) and loss index (r = 0.636, p = 0.0011) after DCA. Immunoreactivity to CRP in coronary atheromatous plaque increases in culprit lesions of unstable angina, and it affects restenosis after DCA. These findings suggest that CRP in atheromatous plaque plays an important role in the pathogenesis of unstable angina and restenosis after coronary intervention.

Tissue factor pathway inhibitor induces expression of JUNB and GADD45B mRNAs

Tissue factor pathway inhibitor (TFPI) is a Kunitz-type protease inhibitor that regulates tissue factor-triggered blood coagulation. It has previously been reported that TFPI inhibits the proliferation of human umbilical vein endothelial cells (HUVECs), suggesting that TFPI may act as more than just a mediator of coagulation through changes in gene expression. By using DNA-array techniques and Northern blot analysis, we here revealed that TFPI transiently induced the mRNA expression of JUNB and GADD45B. The inducible effects were not observed in TFPIdeltaC (lacking the C-terminal basic region) or antithrombin (heparin-binding anticoagulant protease inhibitor). Moreover, the TFPI-induced expression of GADD45B was blocked by receptor-associated protein, which masks the ligand-binding domain of very low density lipoprotein receptor (VLDL-R). In conclusion, this is the first report to show an effect of TFPI on mRNA expression, and suggests that TFPI modulates cellular functions by inducing JUNB and GADD45B expression through binding to VLDL-R.